1. Field of the Invention
The present invention relates to a door opening/closing mechanism for opening and closing a door of, for example, a refrigerator.
2. Description of the Prior Art
A conventionally known door opening/closing mechanism for opening and closing a door of a refrigerator or the like is disclosed, for example, in Japanese Patent Application Laid-Open No. H10-73367. FIGS. 79 and 80 are respectively a sectional view as seen on a horizontal plane and a sectional view as seen from the side of this door opening/closing mechanism. As shown in these figures, a door 301 permits an opening formed in a cabinet 304 to be opened and closed by being pressed against and released from the rim of the opening. The door opening/closing mechanism 300 is fitted on the door 301. On the inner surface of the door 301, a gasket 302 is fitted around the edges thereof. The gasket 302 incorporates a magnet 303, which permits the gasket 302 to be kept in position around the rim of the opening.
The door opening/closing mechanism 300 has an inner handle 310 and an outer handle 311, which are fitted at one side of the door 301 so as to be held by the user. To the inner and outer handles 310 and 311, a grip member 302 is hinge-coupled so as to be rotatable about the axis of a hinge projection 321. At the open end of the grip member 320, a pressing projection 322 is provided. Moreover, on the outer handle 311, a rotary cam 330 is supported so as to be rotatable about a hinge pin 331 when a pressing force is applied to the grip member 320.
On the circumferencial surface of the rotary cam 330, a first and a second contact projection surface 332 and 333 are provided. As the rotary cam 330 rotates, the second contact projection surface 333 makes contact with a slide bar 340 and causes it to slide. The slide bar 340 has, at the tip end thereof, a contact surface 341 having a large area. As the slide bar 340 slides, the contact surface 341 breaks the contact between the gasket 302 and the cabinet 304 that is maintained by the magnetic force of the magnet 303. The slide bar 340 is loaded by a spring 350 with a force that returns the slide bar 340 to its original position when the grip member 320 is released from the pressing force applied thereto.
When the user, with the intention of opening the door 301, holds the inner and outer handles 310 and 311 and presses the grip member 320, the grip member 320 rotates about the hinge projection 321. This causes the pressing projection 322 to move in the direction indicated by arrow B and press the first contact projection surface 332. As a result, the rotary cam 330 rotates counter-clockwise as seen in FIG. 80, and accordingly the slide bar 340, pressed by the second contact projection surface 333, slides.
As a result of the contact surface 341 pressing the front surface of the cabinet 304, the door 301 is opened with a predetermined distance H secured between the cabinet 304 and the gasket 302. At this time, the spring 350 strikes a spring stopper projection 342 provided at the root end of the slide bar 340, and is thereby compressed.
In this state, when the user pulls the inner and outer handles 310 and 311 that the user is holding, the door 301 can be opened without the influence of the magnetic force of the magnet 303 and thus with a comparatively, weak force.
Another conventionally known door opening/closing mechanism that permits a door to be opened and closed at either side (i.e. either at the right-hand or left-hand side) is disclosed in Japanese Patent Application Laid-Open No. H9-303942. In this door opening/closing mechanism, two cam mechanisms for engaging and disengaging a door and a cabinet with and from each other are provided one at either side of the door. FIGS. 81A, 81B, and 81C show the principal portion of one cam mechanism of this door opening/closing mechanism.
The cam mechanism at either side has a lock cam member 402, which is fitted on the cabinet, and a slide cam member 401, which is fitted on the door. On the lock cam member 402, a hinge pin 414 is provided. In the slide cam member 401, a first and a second groove cam 403 and 404 are formed that can move while remaining engaged with the hinge pin 414. When the door is closed, the cam mechanisms at both sides are in a first lock position as shown in FIG. 81A. In this first lock position, the first groove cam 403 lies inclined, and therefore the hinge pin 414 remains engaged with the first groove cam 403 at both sides of the door. Thus, the door is kept closed.
In this state, when the user pulls the door at one side (at the side not illustrated in the figures), in one cam mechanism, the first groove cam 403 moves while remaining engaged with the hinge pin 414 until disengaged therefrom. In the other cam mechanism, as shown in FIG. 81B, the second cam groove 404 moves while remaining engaged with the hinge pin 414 up to a second lock position. At this time, the slide cam member 401 is, at a circular portion 404a of the second groove cam 404, supported by the hinge pin 414. Thus, the door is rotatably locked.
On the lock cam member 402, lock outer cams 411 and. 412 are provided integrally therewith. On the slide cam member 401, slide outer cams 409 and 410 are provided integrally therewith. The lock outer cams 411 and 412 and the slide outer cams 409 and 410 are so arranged as to face each other respectively. These outer cams have pairs of two common cylindrical surfaces (for example, 410a and 412a form one pair, and 410b and 412b another) whose center axis coincides, in the second lock position, with that of the hinge pin, 414 at either side of the door.
When the door rotates about the hinge pin 414, as shown in FIG. 81C, the lock outer cam 412 and the slide outer cam 410 start engaging with and sliding along each other. Thus, the slide outer cam 410 is guided along the cylindrical surface 412a, and, at the side not illustrated in the figures, the slide outer cam 410 is guided along the cylindrical surface 412b. 
Moreover, as the door rotates, a first cam projection 405 provided so as to be concentric with the circular portion 404a slides along and is thereby guided along a second cam projection 406 provided so as to be concentric with the hinge pin 414. This prevents the second groove cam 404 and the hinge pin 414 from being disengaged from each other and thereby permits the door to rotate. In this way, the door can be opened apparently in the same manner as a door having an ordinary one-side opening/closing mechanism. The same Japanese Patent Application discloses also a structure in which the lock outer cams 411 and 412 and the slide outer cams 409 and 410 are abolished and the door is permitted to rotate simply as a result of the first cam projection 405 being guided along the second cam projection 406.
The door opening/closing mechanism disclosed in Japanese Patent Application Laid-Open No. H10-73367 mentioned above requires the user to exert a strong grip when the door 301 is opened at first until the predetermined distance H is secured. Thus, this mechanism is difficult for a person with a weak grip to operate. Even if the grip member 320 is pulled by using the user""s body weight, a considerably strong grip is required at the fingertips. Thus, it is difficult to open the door 301 even by using the user""s body weight.
The force required to operate the mechanism can be reduced by increasing the distance between the first contact projection surface 332 of the rotary cam 330 and the hinge 331. However, this requires the rotary cam 330 as a whole to be made larger and thus gives the mechanism an unsightly design. Moreover, the grip member 320 needs to be moved through a longer distance, which spoils ease of operation. Furthermore, the very structure of this door opening/closing mechanism requires the slide bar 340 to be disposed near the grip member 320, which imposes restrictions on the design of the door opening/closing mechanism.
These problems are encountered also in the door opening/closing mechanism disclosed in Japanese Patent Application Laid-Open No. H9-303942 mentioned above that permits a door to be opened and closed at either side. Moreover, in this door opening/closing mechanism, as the door slides to the second lock position, friction occurs between the door and the lock cam member 402, and in addition it is necessary to slide the gasket 302 that is kept in close contact with the cabinet 304 by the magnet 303 (see FIG. 79). Thus, operation of this mechanism requires an even stronger force.
Furthermore, if the distance between the two slide cam members 401 happens to vary so as to become greater than the interval between the hinge pins 414 provided at both sides of the door, it becomes difficult to open and close the door. For example, the interval between the right-hand and left-hand slide cam members 401 may vary due to the errors that occur when the slide cam members 401 are fitted on a support member and due to the accuracy with which this support member is produced. Moreover, in cases where the door has its inside formed into an integrally foamed heat insulator filled with polyurethane foam, the interval between the right-hand and left-hand slide cam members 401 may vary also due to the variation of ambient temperature and of foaming scale in the foaming process.
In this condition, at the side at which the door is open (i.e. at the side not illustrated in the figures), the first groove cam 403 is guided by the hinge pin 414, and, at the fulcrum side of the door (i.e. at the side illustrated in the figures), the circular portion 404a of the second groove cam 404 is supported by the hinge pin 414. Accordingly, if the interval between the slide cam members 401 differs from the interval between the hinge pins 414 at both sides, high friction occurs between the hinge pin 414 and the first groove cam 403, and thus opening and closing the door requires a strong force.
Moreover, before the lock outer cam 412 engages with the slide outer cam 410, the hinge pin 414 is supported solely by the second grovel cam 404. If the position of the slide cam member 401 varies, the distance through which the second groove cam 404 moves in the direction of the width of the door when the door is opened becomes shorter. Thus, the hinge pin 414 can barely slide along less than half the circumference of the circular portion 404a. 
As a result, the hinge pin 414 cannot be supported by the second groove cam 404, and the resulting variation of the position of the rotation axis makes it impossible for the door to rotate smoothly. In the structure where the lock outer cam 412 and the slide outer cam 410 are abolished, there is even a risk that the hinge pin 414 at the rotation-axis side moves closer to the first groove cam 403 and causes the door to come off.
Furthermore, the slide outer cam 410 that slides along the lock outer cam 412 as the door rotates is located so as to face the lock outer cam 412 before being engaged therewith. Therefore, if there is a large variation, due to an assembly error, in the position in which the slide cam member 401 is fitted, as the door rotates, the slide outer cam 410 collides with the lock outer cam 412, and thereby makes it impossible to open the door smoothly. This requires adjustment of the fitting position or exchange of the support member, and thus leads not only to low production efficiency but also to a low manufacturing yield by making the support member for supporting the slide cam member 401 useless.
Even if the slide cam members 401 are fitted without any assembly error so as to permit the door to be opened and closed smoothly, similar problems arise depending on the environment in which the refrigerator or the like that incorporates the door opening/closing mechanism is used. For example, as ambient temperature rises, the support member on which the slide cam members 401 are fitted expands, and thus the interval between the slide cam members 401 becomes longer. This makes it impossible to open and close the door smoothly, and also leads to a low manufacturing yield.
An object of the present invention is to provide a door opening/closing mechanism that permits a door to be opened with a weak force but nevertheless has an acceptable design.
Another object of the present invention is to provide a door opening/closing mechanism that can be manufactured with improved production efficiency and with an improved manufacturing yield and to provide a manufacturing method of such a door opening/closing mechanism.
To achieve the above objects, according to one aspect of the present invention, a door opening/closing mechanism fitted on a door that closes and opens an opening formed in the body of an apparatus by being brought into and out of contact with the rim of the opening is provided with: a lever mechanism that brings the door a predetermined distance away from the rim of the opening by exploiting the action of a lever.
According to another aspect of the present invention, in this door opening/closing mechanism, the lever mechanism is provided with a handle fitted on the door so as to be rotatable about a rotation axis in such a way that the operated portion of the handle serves as the point of effort of the lever mechanism and the rotation axis serves as the fulcrum of the lever mechanism; and an arm that rotates concentrically with the rotation axis in synchronism with the rotation of the handle in such a way that the point at which the arm makes contact with the rim of the opening serves as the point of load of the lever mechanism. Here, when the handle is operated, the arm presses a portion of the rim of the opening and thereby causes the door to be brought the predetermined distance away from the body.
According to another aspect of the present invention, the door opening/closing mechanism described above first is further provided with: cam mechanisms that permit the door to engage with and disengage from the body at either of the right and left sides of the door. The cam mechanisms can be brought into a first lock position in which they lie symmetrically at both sides of the door and into a second lock position in which they lie symmetrically at both sides of the door. Here, when the door is closed, the cam mechanisms at both sides are kept in the first lock position and, when the door is opened at one side, the door slides and thereby causes the cam mechanism at the other side to be brought into the second lock position.
According to another aspect of the present invention, a door opening/closing mechanism fitted on a door that closes and opens an opening formed in the body of an apparatus by being brought into and out of contact with the rim of the opening is provided with: cam mechanisms that permit the door to engage with and disengage from the body at either of the right and left sides of the door. The cam mechanisms can be brought into a first lock position in which they lie symmetrically at both sides of the door and into a second lock position in which they lie symmetrically at both sides of the door. The cam mechanisms are each provided with: a hinge pin that serves as a rotation axis in the second lock position; and a groove cam that engages with the hinge pin in such a way as to be movable relative to the hinge pin. The groove cam has a slide portion on which a part of the innermost portion of the hinge pin slides when the cam mechanism is moved from the first lock position to the second lock position. Here, when the door is closed, the cam mechanisms at both sides are kept in the first lock position and, when the door is opened at one side, the door slides and thereby causes the cam mechanism at the other side to be brought into the second lock position so as to be rotatably locked in the second lock position.
According to another aspect of the present invention, a door opening/closing mechanism fitted on a door that closes and opens an opening formed in the body of an apparatus by being brought into and out of contact with the rim of the opening is provided with: cam mechanisms that permit the door to engage with and disengage from the body at either of the right and left sides of the door. The cam mechanisms can be brought into a first lock position in which they lie symmetrically at both sides of the door and into a second lock position in which they lie symmetrically at both sides of the door. The cam mechanisms are each provided with: a groove cam formed in the body and guided by the rotation axis of the door; a lock outer cam formed on the body and having two slide surfaces with cross sections shaped like arcs described about the rotation axis at one and the other sides, respectively, of the door; and a slide outer cam formed on the door, having two slide surfaces with cross sections shaped like arcs described about the rotation axis at one and the other sides, respectively, of the door, and guided by the lock outer cam in the second lock position so as to slide on the lock outer cam. Here, when the door is closed, the cam mechanisms at both sides are kept in the first lock position and, when the door is opened at one side, the door slides and thereby causes the cam mechanism at the other side to be brought into the second lock position so as to be rotatably locked in the second lock position. Moreover, at the side at which the cam mechanism is kept in the second lock position when the door is opened, the distance between the point of contact at which a center line through the rotation center of the door is tangent to the portion of the lock outer cam facing the slide outer cam before they starts sliding on each other and the point of contact at which a center line through the rotation center of the door is tangent to the portion of the slide outer cam facing the lock outer cam before they starts sliding on each other, as measured in a radial direction when they are sliding on each other, is made greater than the maximum permissible variation in the outermost distance between the two groove cams formed at both sides of the door.
According to another aspect of the present invention, in a method of manufacturing a door opening/closing mechanism fitted on a door that closes and opens an opening formed in the body of an apparatus by being brought into and out of contact with the rim of the opening, the door opening/closing mechanism is provided with: cam mechanisms that permit the door to engage with and disengage from the body at either of the right and left sides of the door. The cam mechanisms can be brought into a first lock position in which they lie symmetrically at both sides of the door and into a second lock position in which they lie symmetrically at both sides of the door. The cam mechanisms are each provided with: a hinge pin that serves as a rotation axis in the second lock position; a groove cam that engages with the hinge pin in such a way as to be movable relative to the hinge pin; a lock outer cam formed on the body and having two slide surfaces with cross sections shaped like arcs described about the rotation axis at one and the other sides, respectively, of the door; and a slide outer cam formed on the door, having two slide surfaces with cross sections shaped like arcs described about the rotation axis at one and the other sides, respectively, of the door, and guided by the lock outer cam so as to slide on the lock outer cam in such a way as to describe an arc. The door opening/closing mechanism functions in such a way that, when the door is closed, the cam mechanisms at both sides are kept in the first lock position and that, when the door is opened at one side, the door slides and thereby causes the cam mechanism at the other side to be brought into the second lock position so as to be rotatably locked in the second lock position. Here, the method of manufacturing the door opening/closing mechanism includes: a step of setting the design value of the distance, as measured when the tip of the lock outer cam and the tip of the slide outer cam make contact with a straight line parallel to the direction of the width of the body, between the points of contact at which the lock outer cam and the slide outer cam make contact with the straight line to be greater than the maximum permissible variation in the outermost distance between the two groove cams formed at both sides of the door; and a step of manufacturing the door opening/closing mechanism on the basis of the design value.